John Sturgeon and the state of Alaska argued the National Park Service didn't have jurisdiction over a river that flowed through a national preserve. The high court agreed.

The National Park Service can’t tell an Alaskan moose hunter to keep his hovercraft off a river that flows through a national preserve, the Supreme Court ruled Tuesday in a long-running case that pitted the state government and hunters against environmental groups and the federal agency.

John Sturgeon’s dispute with the Park Service dates back to 2007, when rangers he encountered on the Nation River told him his hovercraft—a boat that can glide over water or wetlands on a cushion of air—could not be used on water flowing through the Yukon-Charley Rivers National Preserve. Unlike the state of Alaska, the Park Service bans hovercraft, saying they allow people to get to remote locations that would be spoiled by “motorized equipment.”

While Sturgeon turned back that day, he later sued in 2011, arguing that the federal government was ignoring part of the Alaska National Interest Lands Conservation Act of 1980, which gave the state and its residents special privileges as federal parks were established and expanded. The state of Alaska supported the lawsuit, saying in a brief this summer that it doesn’t make sense to ban hovercraft in a place where people need access to wilderness areas, often using rivers to get to distant communities.

For its part, the Parks Service argued that federal law gives the agency the power to regulate what happens on "navigable waters" in national parks, even when the land beneath those waters is owned by the state.

Writing in a unanimous opinion, Justice Elena Kagan agreed with Sturgeon that the federal law that set aside 104 million acres of land in Alaska for preservation constrained the authority of the Park Service on land or waters not owned by the federal government. In part, that's because when national preserves were set up, they included millions of acres of state, native and private land that aren't completely regulated by the federal agency. The Nation River is included in that exemption.

“That means Sturgeon can again rev up his hovercraft in search of moose,” Kagan wrote.

Last summer a group of nine states filed a brief saying they were concerned that the 9th U.S. Circuit Court of Appeals' decision in 2017 siding with the Park Service over Sturgeon could affect water rights outside of Alaska. But Kagan explained that she saw this case as Alaska-specific.

“If Sturgeon lived in any other State, his suit would not have a prayer of success,” Kagan wrote, underscoring that federal law is clear about the Park Service’s authority over navigable waters like the Nation River within national parks in other states. “Except that Sturgeon lives in Alaska. And as we have said before, ‘Alaska is often the exception, not the rule.’”

In a brief filed last year, environmental groups, including the Sierra Club and National Parks Conservation Association, argued that the Park Service being able to regulate what happens on navigable waters within parks is a key part of preserving the areas in Alaska protected by federal law.

Justice Sonia Sotomayor in a concurring opinion raised the question about whether the limitations of the Sturgeon decision could "engender uncertainty" about the Park Service's larger authority to protect federal park land, and rivers, in Alaska.

"If this is not what Congress intended, Congress should amend ANILCA to clarify the scope of the Service's authority," Sotomayor said. Later, however, the justice wrote that she believes the Park Service still maintains some power to regulate waters if that is needed to protect the parks, such as from pollution. In the court opinion, Kagan seems to agree that the Park Service maintains a "reserved water right" that would, for example, allow the agency to prohibit depletion of a river's water, just not decide what happens on that water.

Mike Litterst, chief spokesperson for the Park Service, said agency officials are "reviewing the decision to determine what changes will be necessary to bring existing policy in line with today's ruling."

In a statement, Doug Vincent-Lang, the commissioner of the Alaska Department of Fish and Game, was one of many state officials who embraced the ruling, saying that in the state "our waterways are our lifeblood. Management authority impacts fishing, hunting, transportation and economic development—all the things Alaskans hold dear."

Matt Findley, the attorney representing Sturgeon through two reviews by the Supreme Court, heralded the decision as important for his client and the state.

"In Alaska, given the vast scope of the landscape, having the appropriate balance between state and federal authorities over these lands and waters is critical," he said, noting that the state has repeatedly underscored that many people use the rivers as roads in remote parts of Alaska. "Preserving the state’s authority to make local calls on the ground about appropriate land management and appropriate land use and water use is critically important in a way that is vastly different than somewhere in California or Virginia."

Laura Maggi is Managing Editor of Route Fifty and is based in Washington, D.C.